How are calories calculated?

Calories are surprisingly hard to pin down. Unless you ride with a power meter, every calorie number in every app — Cadence, Strava, Apple, Garmin — is an educated estimate, and no two apps will ever agree exactly. Here’s how Cadence does it, so you know what your numbers mean.

The three numbers: Active, Basal, and Total

Cadence now shows calories as three separate numbers:

Basal — the calories your body burns just to stay alive during the ride: heart beating, breathing, staying warm. You’d burn these even sitting still. (Other apps sometimes call this “resting.”)
Active — the extra calories from the actual effort of riding or running.
Total — Active + Basal added together. This is the big number, and it’s what most apps and your Apple Watch show.

Each one is available as its own data field on your screens and as a voice announcement, so you can watch whichever you care about.

If you have a power meter (most accurate)

A power meter measures exactly how hard you’re pedaling, in watts — by far the most accurate way to estimate calorie burn. If you’ve added a power meter, Cadence uses only the power meter for calories and ignores all the estimating below.

That also means if your power meter disconnects or stops sending during a ride, that stretch counts resting (Basal) calories only, just as your power reads 0 W. Cadence won’t fill the gap with an estimate, because mixing guesses into real power data muddies it. Keep the meter connected; its data fields show Connecting… or a warning icon when it isn’t.

Sensor choices are saved with each bike. If you ride the same bike on an indoor trainer and outdoors, deselect the trainer before riding outside, or set the outdoor bike up as its own gear. Otherwise Cadence waits for a power meter that never connects, and the ride counts resting calories only.

If you don’t have a power meter (the estimate)

Outdoors, Cadence calculates estimated power and works out roughly how many watts it took to move you down the road, using real physics — the same forces a power meter would feel:

Your weight (you + your bike)
Your speed
The hills: climbing takes far more energy than flat or downhill.
Air resistance: the biggest force at speed; depends on how you’re sitting (see Riding Position below) and on your size, since a taller or heavier rider catches more wind.
Rolling resistance: how much the road drags your tires (see Road Surface below). The CdA number shown next to each position is adjusted for your height and weight.

It then turns those watts into calories exactly like it would for a power meter. It’s an estimate, but a good one — it’s tuned to land within a few percent of real power-meter data.

How watts become calories: your body is only about 20–25% efficient, so most of the energy you burn becomes heat rather than motion. One food calorie is 4.184 kJ, so the two nearly cancel out, and 1 kJ of work at the pedals is about 1 calorie burned. It’s the standard rule for power meters, and Strava uses the same approach. The rule fits an average-size rider making a real effort, so for larger riders on easy rides it likely reads somewhat low.

If your calories look lower than before: they probably are. Older versions of this estimate ran high; the new one is much more accurate. The lower number is the more honest one, not a bug.

Indoor rides without a power meter (heart rate)

Indoors, that physics estimate often has nothing to work with. On a spin bike or a basic trainer without a speed sensor there’s no speed to estimate from, so the ride would count resting calories only, even with a heart rate strap on.

So for indoor rides without a power meter, Cadence estimates calories from your heart rate using the published Keytel equation. It needs:

An indoor ride with no power meter added
Heart rate, from a Bluetooth heart rate sensor or your Apple Watch
Your Sex and Birth Date set in Settings ▸ Profile ▸ Body Metrics

If any of those is missing, Cadence falls back to the physics estimate above (using a speed sensor if you have one), or to resting calories only if there’s no speed either.

Heart rate still reads high. It can substantially overestimate calories: in two indoor test rides its totals were roughly 30–50% above the power meter’s, and errors can be larger. The equation was developed and validated on adults during steady exercise. If you want accurate indoor numbers, a power meter or a smart trainer that reports power is the way to get them. Outdoors, Cadence never uses heart rate for calories; the physics estimate is much closer to real power-meter data.

Your bike settings: Settings ▸ Gear ▸ (your bike)

Two of those forces depend on your specific bike and how you ride it, so you can set them per bike. Cadence starts everyone on sensible defaults (a road bike, hands on the hoods, regular asphalt), so you only need to touch these if they don’t match you:

Riding Position: how you usually sit. Sitting up catches a lot of wind and burns more; on the hoods is the middle; in the drops or on aero bars is more slippery and burns less.
Road Surface: smooth asphalt rolls easily; rough/chipseal and gravel drag more and burn more.
E-Bike Compensation: if your bike has a motor, the motor does part of the work, so you burn fewer calories. Pick the assist you normally use (Light, Medium, or Heavy) and Cadence lowers the estimate to match. Leave it on None for a regular bike.

These only affect the physics estimate. With a power meter your real effort is already measured, motor or not, and heart rate already reflects your own effort.

Your body: Settings ▸ Profile ▸ Body Metrics

The Basal (resting) number uses a well-established formula (Mifflin-St Jeor) that needs your weight, height, age, and sex. Your height and weight also size the air resistance in the estimate. If you leave them blank, Cadence assumes an average rider (165 lb, 5’10”). Filling these in makes your resting calories accurate for your body. If you leave height or sex blank, Cadence falls back to a simpler weight-only estimate. It still works, just less precisely. Sex and Birth Date also turn on the heart-rate estimate for indoor rides.

Running

For runs, Cadence uses a research-based model (Minetti) that accounts for grade, so running uphill correctly costs more than running flat, and steep downhills cost the least.

Apple Watch “Watch Only” workouts

If you record on your Apple Watch without your iPhone (“Watch Only”), Cadence uses Apple’s own built-in workout calorie calculation, not the method above.

Why don’t my calories match Strava, Apple, or Garmin?

They won’t, and that’s expected. Every app uses a different method: Garmin licenses a dedicated algorithm (from Firstbeat, which they now own), and Strava and Apple have their own. Without a power meter there’s no single “correct” number, so different tools will always land in different places.

Because of this, Cadence doesn’t send its calorie number to Strava by default, it lets Strava calculate its own from your ride data. If you’d rather Strava show Cadence’s number, turn on Settings ▸ Strava ▸ Include Calories.

Why did an old ride’s calories change?

When you open an activity recorded before this update, Cadence recalculates it with the new model, so its total may differ from what you saw before. This is expected and the new number is the more accurate one. Editing a ride also recalculates it when you change something the estimate depends on, such as indoor or outdoor, your weight or height, or the bike.